Sea water under an East Antarctic ice shelf showed no sign of higher temperatures despite fears of a thaw linked to global warming that could bring higher world ocean levels, first tests showed on Monday.

Sensors lowered through three holes drilled in the Fimbul Ice Shelf showed the sea water is still around freezing and not at higher temperatures widely blamed for the break-up of 10 shelves on the Antarctic Peninsula, the most northerly part of the frozen continent.

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"The water under the ice shelf is very close to the freezing point," Ole Anders Noest of the Norwegian Polar Institute wrote in a statement after drilling through the Fimbul, which is between 250 meters and 400 meters (820-1,310 ft) thick.

"This situation seems to be stable, suggesting that the melting under the ice shelf does not increase," he wrote of the first drilling cores.

The findings, a rare bit of good news after worrying signs in recent years of polar warming, adds a small bit to a puzzle about how Antarctica is responding to climate change, blamed largely on human use of fossil fuels.

Antarctica holds enough water to raise world sea levels by 57 meters (187 ft) if it ever all melted, so even tiny changes are a risk for low-lying coasts or cities from Beijing to New York.

The Institute said the water under the Fimbul was about -2.05 Celsius (28.31 Fahrenheit) -- salty water freezes at a slightly lower temperature than fresh water.

And it was slightly icier than estimates in a regional computer model for Antarctica, said Nalan Koc, head of the Norwegian Polar Institute's Center for Ice, Climate and Ecosystems.

"The important thing is that we are now in a position to monitor the water beneath the ice shelf," she told Reuters. "If there is a warming in future we can tell."